In this application, the P.I. proposes a series of aims designed to address the localization of ASH1 mRNA in yeast cells. Ash1p is an asymmetrically localized protein, important in repressing mating type switching in the daughter cell. The asymmetry of this nuclear protein results from the localization of its mRNA at the distal cortex of a daughter cell, the bud, and the greater accumulation of this negative regulator of gene expression in daughter nuclei. In the first aim, cis-acting sequences and trans-acting factors will be isolated in order to determine the protein components of the mechanism. Specific aim 2 proposes experiments to follow the transport, export and localization of this RNA from the site of its transcription to its final location at the cortex of the bud. In the final specific aim, the mechanism of nuclear export will be assessed to determine points in the pathway where rate-limitations may exist.